The construction of the girder just above the existing Shinkansen viaduct in urban area

We are now carrying out a project to open new line ""Ueno-Tokyo line'', which connects two radiate railway lines. This line is now under construction just above the in-service Shinkansen line, because we couldn't obtain the space for new line in urban area. We applied a viaduct structure with double- deck system, which consisted of a viaduct for the new line added on the existing viaduct for Shinkansen. The construction site was so narrow, that we couldn't get the sufficient space for using a large size crane. Therefore, we specially manufactured a huge movable erection girder, and a push-out method was applied to construct the main girders by using the movable erection girder. We completed all of the girder constructions with high difficulty without any accidents by carrying out elegant design and construction. In this paper, we describe the construction of the girders between piers of new viaduct just above the Shinkansen line.